<template>
  <el-scrollbar height="100vh">
    <div class="container">
      <el-affix :offset="1">
        <h1 class="title">按限制范围加载图层</h1>
      </el-affix>
      <div id="map" class="map-x" ref="mapBox"></div>
      <div class="codestyle"><Code /></div>
    </div>
  </el-scrollbar>
</template>
<script>
import { toRefs, reactive, ref, onMounted } from 'vue-demi'
import Code from './code.vue'
import 'ol/ol.css'
import { Map, View } from 'ol'
import Tile from 'ol/layer/Tile'
import XYZ from 'ol/source/XYZ'
export default {
  setup () {
    const state = reactive({
      map: ref(null),
      mapBox: ref(null)
    })

    const init = () => {
      const xyz = new Tile({
        source: new XYZ({
          url: 'https://api.maptiler.com/maps/basic-4326/256/{z}/{x}/{y}.png?key=B3EG5uYPUvFucEWVoCa3',
          crossOrigin: 'anonymous'
        })
      })

      state.map = new Map({
        target: state.mapBox,
        layers: [xyz],
        view: new View({
          // 地图视图
          projection: 'EPSG:4326', // 坐标系，有EPSG:4326和EPSG:3857
          center: [120.390733, 36.123837], // 北京坐标
          zoom: 7 // 地图缩放级别（打开页面时默认级别）
        })
      })

      xyz.on('postrender', event => {
        var ctx = event.context
        ctx.save()
        var pixelRatio = event.frameState.pixelRatio
        var size = state.map.getSize()
        // 平移
        ctx.translate(size[0] / 2 * pixelRatio, size[1] / 2 * pixelRatio)
        // 缩放
        ctx.scale(3 * pixelRatio, 3 * pixelRatio)
        // 平移
        ctx.translate(-75, -80)
        ctx.beginPath()
        ctx.moveTo(75, 40)
        ctx.bezierCurveTo(75, 37, 70, 25, 50, 25)
        ctx.bezierCurveTo(20, 25, 20, 62.5, 20, 62.5)
        ctx.bezierCurveTo(20, 80, 40, 102, 75, 120)
        ctx.bezierCurveTo(110, 102, 130, 80, 130, 62.5)
        ctx.bezierCurveTo(130, 62.5, 130, 25, 100, 25)
        ctx.bezierCurveTo(85, 25, 75, 37, 75, 40)
        ctx.clip()
        ctx.translate(75, 80)
        ctx.scale(1 / 3 / pixelRatio, 1 / 3 / pixelRatio)
        ctx.translate(-size[0] / 2 * pixelRatio, -size[1] / 2 * pixelRatio)
      })

      xyz.on('rendercomplete', function (event) {
        var ctx = event.context
        ctx.restore()
      })
    }

    onMounted(() => {
      init()
    })

    return {
      init,
      ...toRefs(state)
    }
  },
  components: {
    Code
  }
}
</script>
<style lang="scss" scoped>
@import '../../css/main.scss';
.select {
  margin: 20px 0;
}
</style>
